Gas turbine engines are well-known for providing propulsion and power production. Conventionally, a gas turbine engine consists of an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in between.
A conventional gas turbine engine 30 is depicted in FIG. 1. Ambient air is received at the inlet of the compressor 3, where it is compressed and forced at a substantially higher pressure and temperature into the combustion chamber 7. There, the compressed air is mixed with fuel and burned, thus further increasing the temperature and pressure by confining the volume into the combustion chamber 7. The resultant combustion gases are then passed through the hot turbine section 5, where mechanical shaft power may be extracted to drive a shaft 27, which couples the turbine 5 with the compressor 3. The remaining exhaust gas pressure is typically used to provide thrust by exhausted in rearward direction.
FIG. 2 shows a detailed cross-sectional view of an upper-half section of the gas turbine engine 30 shown in FIG. 1. Ambient air is taken from compressor inlet 32 where the compressor 3 increases the pressure and temperature until the compressor outlet 36. After this point, compressed air is delivered to the combustion chamber 7 where temperature is increased. Dashed line 33 depicts the hot fluid channel communicating the combustion chamber 7 with the turbine 5, which comprises stators 8, 10 and rotors 9, 11, alternatively positioned along the turbine 5 section. Power is extracted by the turbine 5 from the fluid to the rotatory assembly or to the shaft 27, which mechanically couples the turbine 5 with the compressor 3. Therefore, the power extracted by the turbine 5 is transfer throughout the shaft 27 to the compressor 3, and to other applications required by the aircraft. After the turbine 5, the fluid is delivered downstream by the hot fluid channel 33.
The mentioned cycle may be notably improved by including a dedicated device, traditionally known as heat exchanger or recuperator. Heat exchangers are often used in combination with the combustion stage to recover some of the wasted energy in the exhaust. The wasted heat is transferred to the compressed air, thus preheating it before entering into the combustion chamber. The pre-heated compressed air requires less fuel to heat the mixture of compressed air and fuel up to the turbine inlet temperature. This way, the heat exchanger offers a gas turbine engine more efficient.
FIG. 3 depicts a gas turbine engine 35 with a heat exchanger 23. Ambient air is taken at the inlet of the compressor 3, where it is compressed and forced at a substantially higher pressure and temperature to the heat exchanger 23. In the heat exchanger 23, the compressed air temperature is increased by the fluid delivered by the turbine 5, thus transferring energy between both fluids. Fluid from heat exchanger 23 is conducted to the combustion chamber 7, where fluid temperature is increased. After the combustion chamber 7, fluid is conducted to the turbine 5, at least one turbine stage, where power is transferred from the fluid to the mechanical shaft 27. After the turbine 5, the fluid is delivered to the heat exchanger 23 to be finally delivered to the exterior. The heat exchanger 23 extracts energy from fluid, circulating from the turbine 5 towards the exterior. As in FIGS. 1 and 2, the compressor 3 and the turbine 5 are mechanically coupled by a shaft 27. Power extracted by the turbine 5 is used to provide power to the compressor 3, as well as to provide power to required applications.
However, incorporating a heat exchanger in a gas turbine engine carries some disadvantages, such as an increase in weight, complexity, and cost.
Therefore, it would be desirable to provide technical means for improving the efficiency of a gas turbine engine, without requiring the use of dedicated devices, such as heat exchangers, which involve an increase in weight and cost.
Additionally, it would be desirable to extend these technical means to all aircraft gas turbine engines, such as the main engines and the auxiliary power unit, in such a way that the commonality and reuse of conventional gas turbine engine components are maximized.